Rework codegen for GraphQL objects and subscriptions (#971, #421)

- preserve and reuse defined impl blocks in #[graphql_object] and #[graphql_subscription] macros expansion
- allow renaming `ScalarValue` type parameter in expanded code via `scalar = S: ScalarValue` syntax

Additionally:
- rename `rename` attribute's argument to `rename_all`
- support `rename_all` in #[graphql_interface] macro

Author: tyranron

docs/book/content/advanced/implicit_and_explicit_null.md

@@ -99,10 +99,11 @@ impl Into<UserPatch> for UserPatchInput {
 struct Context {
     session: Session,
 }
+impl juniper::Context for Context {}
 
 struct Mutation;
 
-#[juniper::graphql_object(Context=Context)]
+#[juniper::graphql_object(context = Context)]
 impl Mutation {
     fn patch_user(ctx: &Context, patch: UserPatchInput) -> FieldResult<bool> {
         ctx.session.patch_user(patch.into())?;

docs/book/content/advanced/subscriptions.md

@@ -25,10 +25,6 @@ This example shows a subscription operation that returns two events, the strings
 sequentially: 
 
 ```rust
-# extern crate futures;
-# extern crate juniper;
-# extern crate juniper_subscriptions;
-# extern crate tokio;
 # use juniper::{graphql_object, graphql_subscription, FieldError};
 # use futures::Stream;
 # use std::pin::Pin;
@@ -40,7 +36,7 @@ sequentially:
 # pub struct Query;
 # #[graphql_object(context = Database)]
 # impl Query {
-#    fn hello_world() -> &str {
+#    fn hello_world() -> &'static str {
 #        "Hello World!"
 #    }
 # }
@@ -110,7 +106,7 @@ where [`Connection`][Connection] is a `Stream` of values returned by the operati
 # 
 # #[graphql_object(context = Database)]
 # impl Query {
-#     fn hello_world() -> &str {
+#     fn hello_world() -> &'static str {
 #         "Hello World!"
 #     }
 # }

docs/book/content/quickstart.md

@@ -6,11 +6,9 @@ Juniper follows a [code-first approach][schema_approach] to defining GraphQL sch
 
 ## Installation
 
-!FILENAME Cargo.toml
-
 ```toml
 [dependencies]
-juniper = { git = "https://github.com/graphql-rust/juniper" }
+juniper = "0.15"
 ```
 
 ## Schema example
@@ -89,7 +87,7 @@ struct Query;
     context = Context,
 )]
 impl Query {
-    fn apiVersion() -> &str {
+    fn apiVersion() -> &'static str {
         "1.0"
     }
 
@@ -114,14 +112,13 @@ struct Mutation;
 
 #[graphql_object(
     context = Context,
-
     // If we need to use `ScalarValue` parametrization explicitly somewhere
-    // in the object definition (like here in `FieldResult`), we should
+    // in the object definition (like here in `FieldResult`), we could
     // declare an explicit type parameter for that, and specify it.
-    scalar = S,
+    scalar = S: ScalarValue + Display,
 )]
-impl<S: ScalarValue + Display> Mutation {
-    fn createHuman(context: &Context, new_human: NewHuman) -> FieldResult<Human, S> {
+impl Mutation {
+    fn createHuman<S: ScalarValue + Display>(context: &Context, new_human: NewHuman) -> FieldResult<Human, S> {
         let db = context.pool.get_connection().map_err(|e| e.map_scalar_value())?;
         let human: Human = db.insert_human(&new_human).map_err(|e| e.map_scalar_value())?;
         Ok(human)

docs/book/content/types/interfaces.md

@@ -232,6 +232,21 @@ trait Character {
 # fn main() {}
 ```
 
+Renaming policies for all [GraphQL interface][1] fields and arguments are supported as well:
+```rust
+# #![allow(deprecated)]
+# extern crate juniper;
+use juniper::graphql_interface;
+
+#[graphql_interface(rename_all = "none")] // disables any renaming
+trait Character {
+    // Now exposed as `my_id` and `my_num` in the schema
+    fn my_id(&self, my_num: i32) -> &str;
+}
+#
+# fn main() {}
+```
+
 
 ### Custom context
 

docs/book/content/types/objects/complex_fields.md

@@ -3,9 +3,10 @@
 If you've got a struct that can't be mapped directly to GraphQL, that contains
 computed fields or circular structures, you have to use a more powerful tool:
 the `#[graphql_object]` procedural macro. This macro lets you define GraphQL object
-fields in a Rust `impl` block for a type. Note that only GraphQL fields
-can be specified in this `impl` block. If you want to define normal methods on the struct,
-you have to do so in a separate, normal `impl` block. Continuing with the
+fields in a Rust `impl` block for a type. Note, that GraphQL fields are defined in 
+this `impl` block by default. If you want to define normal methods on the struct,
+you have to do so either in a separate "normal" `impl` block, or mark them with
+`#[graphql(ignore)]` attribute to be omitted by the macro. Continuing with the
 example from the last chapter, this is how you would define `Person` using the
 macro:
 
@@ -28,12 +29,15 @@ impl Person {
     fn age(&self) -> i32 {
         self.age
     }
+
+    #[graphql(ignore)]
+    pub fn hidden_from_graphql(&self) {
+        // [...]
+    }
 }
 
-// Note that this syntax generates an implementation of the GraphQLType trait,
-// the base impl of your struct can still be written like usual:
 impl Person {
-    pub fn hidden_from_graphql(&self) {
+    pub fn hidden_from_graphql2(&self) {
         // [...]
     }
 }
@@ -44,7 +48,6 @@ impl Person {
 While this is a bit more verbose, it lets you write any kind of function in the
 field resolver. With this syntax, fields can also take arguments:
 
-
 ```rust
 # extern crate juniper;
 # use juniper::{graphql_object, GraphQLObject};
@@ -61,7 +64,7 @@ struct House {
 
 #[graphql_object]
 impl House {
-    // Creates the field inhabitantWithName(name), returning a nullable person
+    // Creates the field `inhabitantWithName(name)`, returning a nullable `Person`.
     fn inhabitant_with_name(&self, name: String) -> Option<&Person> {
         self.inhabitants.iter().find(|p| p.name == name)
     }
@@ -127,15 +130,29 @@ impl Person {
 # fn main() { }
 ```
 
+Or provide a different renaming policy on a `impl` block for all its fields:
+```rust
+# extern crate juniper;
+# use juniper::graphql_object;
+struct Person;
+
+#[graphql_object(rename_all = "none")] // disables any renaming
+impl Person {
+    // Now exposed as `renamed_field` in the schema
+    fn renamed_field() -> bool {
+        true
+    }
+}
+#
+# fn main() {}
+```
+
 ## Customizing arguments
 
 Method field arguments can also be customized.
 
 They can have custom descriptions and default values.
 
-**Note**: The syntax for this is currently a little awkward. 
-This will become better once the [Rust RFC 2565](https://github.com/rust-lang/rust/issues/60406) is implemented.
-
 ```rust
 # extern crate juniper;
 # use juniper::graphql_object;
@@ -144,35 +161,46 @@ struct Person {}
 
 #[graphql_object]
 impl Person {
-    #[graphql(
-        arguments(
-            arg1(
-                // Set a default value which will be injected if not present.
-                // The default can be any valid Rust expression, including a function call, etc.
-                default = true,
-                // Set a description.
-                description = "The first argument..."
-            ),
-            arg2(
-                default = 0,
-            )
-        )
-    )]
-    fn field1(&self, arg1: bool, arg2: i32) -> String {
+    fn field1(
+        &self,
+        #[graphql(
+            // Arguments can also be renamed if required.
+            name = "arg",
+            // Set a default value which will be injected if not present.
+            // The default can be any valid Rust expression, including a function call, etc.
+            default = true,
+            // Set a description.
+            description = "The first argument..."
+        )]
+        arg1: bool,
+        // If default expression is not specified then `Default::default()` value is used.
+        #[graphql(default)]
+        arg2: i32,
+    ) -> String {
         format!("{} {}", arg1, arg2)
     }
 }
 #
 # fn main() { }
 ```
 
-## More features
+Provide a different renaming policy on a `impl` block also implies for arguments:
+```rust
+# extern crate juniper;
+# use juniper::graphql_object;
+struct Person;
 
-GraphQL fields expose more features than Rust's standard method syntax gives us:
+#[graphql_object(rename_all = "none")] // disables any renaming
+impl Person {
+    // Now exposed as `my_arg` in the schema
+    fn field(my_arg: bool) -> bool {
+        my_arg
+    }
+}
+#
+# fn main() {}
+```
 
-* Per-field description and deprecation messages
-* Per-argument default values
-* Per-argument descriptions
+## More features
 
-These, and more features, are described more thoroughly in [the reference
-documentation](https://docs.rs/juniper/latest/juniper/macro.object.html).
+These, and more features, are described more thoroughly in [the reference documentation](https://docs.rs/juniper/latest/juniper/attr.graphql_object.html).

docs/book/content/types/objects/defining_objects.md

@@ -152,7 +152,22 @@ struct Person {
     name: String,
     age: i32,
     #[graphql(name = "websiteURL")]
-    website_url: Option<String>, // Now exposed as websiteURL in the schema
+    website_url: Option<String>, // now exposed as `websiteURL` in the schema
+}
+#
+# fn main() {}
+```
+
+Or provide a different renaming policy on a struct for all its fields:
+```rust
+# extern crate juniper;
+# use juniper::GraphQLObject;
+#[derive(GraphQLObject)]
+#[graphql(rename_all = "none")] // disables any renaming
+struct Person {
+    name: String,
+    age: i32,
+    website_url: Option<String>, // now exposed as `website_url` in the schema
 }
 #
 # fn main() {}
@@ -181,9 +196,9 @@ The `name`, `description`, and `deprecation` arguments can of course be
 combined. Some restrictions from the GraphQL spec still applies though; you can
 only deprecate object fields and enum values.
 
-## Skipping fields
+## Ignoring fields
 
-By default all fields in a `GraphQLObject` are included in the generated GraphQL type. To prevent including a specific field, annotate the field with `#[graphql(skip)]`:
+By default, all fields in a `GraphQLObject` are included in the generated GraphQL type. To prevent including a specific field, annotate the field with `#[graphql(ignore)]`:
 
 ```rust
 # extern crate juniper;
@@ -192,9 +207,9 @@ By default all fields in a `GraphQLObject` are included in the generated GraphQL
 struct Person {
     name: String,
     age: i32,
-    #[graphql(skip)]
+    #[graphql(ignore)]
     # #[allow(dead_code)]
-    password_hash: String, // This cannot be queried or modified from GraphQL
+    password_hash: String, // cannot be queried or modified from GraphQL
 }
 #
 # fn main() {}

docs/book/content/types/objects/error_handling.md

@@ -17,8 +17,7 @@ it will bubble up to the surrounding framework and hopefully be dealt with
 there.
 
 For recoverable errors, Juniper works well with the built-in `Result` type, you
-can use the `?` operator or the `try!` macro and things will generally just work
-as you expect them to:
+can use the `?` operator and things will generally just work as you expect them to:
 
 ```rust
 # extern crate juniper;
@@ -36,21 +35,18 @@ struct Example {
 
 #[graphql_object]
 impl Example {
-    fn contents() -> FieldResult<String> {
+    fn contents(&self) -> FieldResult<String> {
         let mut file = File::open(&self.filename)?;
         let mut contents = String::new();
         file.read_to_string(&mut contents)?;
         Ok(contents)
     }
 
     fn foo() -> FieldResult<Option<String>> {
-      // Some invalid bytes.
-      let invalid = vec![128, 223];
+        // Some invalid bytes.
+        let invalid = vec![128, 223];
 
-      match str::from_utf8(&invalid) {
-        Ok(s) => Ok(Some(s.to_string())),
-        Err(e) => Err(e)?,
-      }
+        Ok(Some(str::from_utf8(&invalid)?.to_string()))
     }
 }
 #
@@ -66,7 +62,6 @@ there - those errors are automatically converted into `FieldError`.
 
 Juniper's error behavior conforms to the [GraphQL specification](https://spec.graphql.org/June2018/#sec-Errors-and-Non-Nullability).
 
-
 When a field returns an error, the field's result is replaced by `null`, an
 additional `errors` object is created at the top level of the response, and the
 execution is resumed. For example, with the previous example and the following
@@ -86,12 +81,12 @@ returned:
 
 !FILENAME Response for nullable field with error
 
-```js
+```json
 {
   "data": {
     "example": {
       contents: "<Contents of the file>",
-      foo: null,
+      foo: null
     }
   },
   "errors": [
@@ -120,7 +115,7 @@ following would be returned:
 
 !FILENAME Response for non-null field with error and no nullable parent
 
-```js
+```json
 {
   "errors": [
     "message": "Permission denied (os error 13)",
@@ -162,11 +157,11 @@ struct Example {
 
 #[graphql_object]
 impl Example {
-    fn whatever() -> Result<bool, CustomError> {
-      if let Some(value) = self.whatever {
-        return Ok(value);
-      }
-      Err(CustomError::WhateverNotSet)
+    fn whatever(&self) -> Result<bool, CustomError> {
+        if let Some(value) = self.whatever {
+            return Ok(value);
+        }
+        Err(CustomError::WhateverNotSet)
     }
 }
 #